Conventionally, an injector is applied to a fluid device such as a fuel injection valve and an inkjet printer. In such an injector, small nozzle holes are defined for spraying fluid therethrough. For example, a plate member is blanked to form such small nozzle holes. In this forming method, the plate member is blanked, and small burrs are apt to be left around the blanked portion in the plate member.
Conventionally, such small burrs are removed by grinding an end surface of the blanked plate member. The small burrs may be constantly trimmed by grinding the end surface of the plate member. However, in this case, a grinding device such as a brush needs to be mechanically urged onto the plate member formed with the nozzle holes. In this grinding process, the end section of each nozzle hole is apt to be tucked into the nozzle hole. Consequently, it is difficult to accurately form the end section of the nozzle hole. In addition, when the plate member is applied with chemical polishing such as etching, the shape of the small hole may vary in dependence upon the shape of a burr before being applied with the chemical polishing. Accordingly, it is difficult to accurately form the end section of the nozzle hole, even when the chemical polishing is applied to the plate member. Furthermore, in this chemical polishing, it is difficult to constantly form the end section of the nozzle hole uniformly among multiple plate members. In addition, waste materials such as etching solution may be exhausted after chemical polishing to cause pollution. Additionally, the plate member may be corroded due to being submerged in etching solution.
According to JP-A-6-99581, a small burr is removed from the plate member by grinding or applying a laser beam, after blanking the plate member. However, in JP-A-6-99581, the radiation range of the laser beam is set greater than the nozzle hole such that the laser beam is applied to entirely surround the nozzle hole. Accordingly, large output power is required to apply the laser beam. In addition, the structure of the base material constructing the plate member may be deteriorated due to application of the laser beam with large output power.